碰撞池-多接收电感耦合等离子体质谱分析硅同位素的方法研究

通过更换仪器进样系统、改变溶液基体、调节碰撞气的种类和流量以及调节质量分辨率等参数，建立了碰撞池-多接收电感耦合等离子体质谱（Collision Cell-MC-ICP-MS）测定硅同位素丰度组成的分析方法。实验结果表明:使用PFA雾化器、Pt锥和蓝宝石材质的矩管可有效降低仪器本底；调节狭缝宽度、中心杯位置等可提高仪器的质量分辨率，实现硅同位素离子与同量异位素干扰离子在一定程度上的分离；选择氖气（Ne）和氩气（Ar）的混合气作为碰撞气、降低溶液中四甲基氢氧化铵（TMAH）浓度等能有效降低多原子离子的干扰。在此基础上，分析了样品WASO 04和GBW(E)080272中硅同位素的丰度组成，同位素丰度比R_30/28的测量精度达到0.02%。将样品WASO 04作为参考标准时，样品GBW(E)080272中的硅同位素分馏系数δ³⁰Si为-1.57‰。

Determination of Silicon Isotope Ratios by Collision-Cell Multi-Collectors Inductively Coupled Plasma Mass Spectrometry

The method of analyzing the silicon isotope ratios was developed by collision cell multi-collectors inductively coupled plasma mass spectrometry (MC-ICP-MS). Replacing to PFA nebulizer, Pt cones and sapphire injector were proved to be helpful to decrease the silicon concentration in the instrument; silicon ions were partly separated with interferences after， when the mass resolution was increased by adjusting the slits’ width; using mixture of Neon (Ne) and Argon (Ar) as collision gas and keeping the matrix(TMAH) in lower concentration could efficiently reduce the production of polyatomic ions, which contributed to the decrease of isobaric interferences. Subsequently, the silicon isotope composition of samples WASO 04 and GBW(E)080272 were determined, the uncertainty of this method was about 0.02%, the δ³⁰Si value of GBW(E) 080272 relative to WASO 04 was -1.57‰.